R help - Oct 2003 - GIS re-mapping / polygon overlap

In Germany the Unemployment Agency uses a sectioning of the german map that
is different from the usual Administrative Boundaries. 
Some demographic data are available in Administrative Boundaries only, some
in Unemployment Boundaries only.

I would like to generate estimates in one boundary system of data availabe
in the other boundary system, and would appreciate advice concerning the
following questions:

- can someone provide mapping functions between german Administrative
Boundaries (Kreise, Gemeinden, ...) and Unemployment Boundaries (Arbeits?mter)
OR
  - can someone provide polygon data of Unemployment Boundaries and/or
Administrative Boundaries
  AND
    - is there a general function in R available to map demographic data
between two boundary systems
    OR
    - is there an efficient R function that can determine the amount of area
overlap between two general polygons (beyond gpclib)

I am willing to share developed code for this problem (that's why I would
prefer gpl code over gpclib, which is not really free)

Thanks for any help


Jens Oehlschl?gel


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On Thursday 23 October 2003 13:36, Jens Oehlschl?gel
wrote:
> In Germany the Unemployment Agency uses a sectioning of the german map that
> is different from the usual Administrative Boundaries.
> Some demographic data are available in Administrative Boundaries only, some
> in Unemployment Boundaries only.
>
> I would like to generate estimates in one boundary system of data availabe
> in the other boundary system, and would appreciate advice concerning the
> following questions:
>
> - can someone provide mapping functions between german Administrative
> Boundaries (Kreise, Gemeinden, ...) and Unemployment Boundaries
> (Arbeits?mter) OR
>   - can someone provide polygon data of Unemployment Boundaries and/or
> Administrative Boundaries
>   AND
>     - is there a general function in R available to map demographic data
> between two boundary systems
>     OR
>     - is there an efficient R function that can determine the amount of
> area overlap between two general polygons (beyond gpclib)
>
> I am willing to share developed code for this problem (that's why I
would
> prefer gpl code over gpclib, which is not really free)
>
> Thanks for any help
>
>
> Jens Oehlschl?gel

I am not sure, but it sounds more that you are kooking for a GPL GIS like 
GRASS http://grass.itc.it , have a look at the 5.3/7 development branch (I am 
not sure if it is already usable but 5.0.3 is close to official release), 
they have such things as amount overlap and other gis commands.
Thuban could be worth a try as well,http://freegis.org/index.de.html

cheers Martin

Jens Oehlschl?gel wrote:
>   AND
>     - is there a general function in R available to map demographic data
> between two boundary systems
>     OR
>     - is there an efficient R function that can determine the amount of
area
> overlap between two general polygons (beyond gpclib)
> 
> I am willing to share developed code for this problem (that's why I
would
> prefer gpl code over gpclib, which is not really free)
> 
> Thanks for any help
There is pretty cool polygon intersection algorithm available at:

	http://davis.wpi.edu/~matt/courses/clipping/4th.html

with the code at:

	http://davis.wpi.edu/~matt/courses/clipping/code.html

You can pick up the paper the code is based on from kai hormann's home
page (currently):

	http://vcg.isti.cnr.it/~hormann/

The only problem with the algorithm is that it doesn't handle holes, but 
for area computations you could just join the holes to the boundary.

-- 
Ross Ihaka                         Email:  ihaka at stat.auckland.ac.nz
Department of Statistics           Phone:  (64-9) 373-7599 x 85054
University of Auckland             Fax:    (64-9) 373-7018
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